After the fall of Rome, A.D. 476, trade was an extremely hazardous undertaking as likely to result in death at the hands of pirates as in a handsome profit. By about A.D. 1000, a number of citystates had arisen whose prosperity was based on a revival of trade -Venice, Florence, Genoa, Pisa, Marseille, and Barcelona on the Mediterranean, and the Hansa cities in northern Europe.
By far the wealthiest of these was Venice, whose traders were able to furnish the ships for the Crusades ( A.D. 1095-1270). Venetian traders were thus in a position to demand commercial privileges in the reopened Syrian ports. About 1400, Venice had 3,300 ships in her merchant fleet and navy, manned by 36,000 men.
Venice and other trading cities opened up the old trade routes; they organized the financial institutions to finance their operations, and the later explorations and trade; they suppressed piracy; and they held in check the Moslem tide. Their decline was contemporary with the rise of the national powers, England and the Netherlands, to which the ship and commercial power were to move by way of the Iberian Peninsula.